Monitoring of tire pressure can be assumed to become a standard functionality in vehicles, at least in cars and trucks, not only due to governmental and legal regulations but also in view of a general demand for enhanced vehicle safety.
Generally, tire pressure monitoring can be accomplished directly and indirectly.
In direct tire pressure monitoring, a current pressure in a vehicle tire is directly measured, e.g. by means of a sensor arranged inside the tire. An example for direct tire pressure monitoring is described, e.g., in U.S. Pat. No. 7,111,507 B2.
Indirect tire pressure monitoring uses information, which—in contrast to directly obtained pressure values—is somehow related to the tire pressure. Commonly, such information may be provided by further control and/or detection devices of vehicles, such as ECUs (electronic control unit), antilock braking systems, dynamic stability systems, anti-spin systems and traction control systems, in form of digital and/or analog data and/or signals. The information may include the rotational speed or angular velocity of the tire or its wheel, respectively, which information is then used as basis to calculate or estimate a value representing tire pressure. An example for indirect tire pressure monitoring is described, e.g., in DE 103 60 723 A1.
Particularly indirect tire pressure monitoring requires complex computation and calculation to derive tire pressure from pressure related information. Moreover, the connection between pressure related information and tire pressure is prone to external influences, such as current driving situations and road conditions.
Also, vehicle specific conditions may influence tire pressure and information related thereto. For example, current conditions of suspension means or system(s) of a vehicle may affect tire pressure and, thus, results of tire pressure monitoring. This is particularly possible for indirect tire pressure monitoring.